Tube for pneumatic tires.



W. A. VAIL & 0. E. SMITH.

TUBE POR PNEUMATIG TIRES.

APPLICATION FILED AUG. s, 1913.

Patented Mar. 3l, 191% Zia -ffso of the.tube,-that'is, the side towardthe een-YV ter of the-wheelbein'g, as hereinafter ex v I vsure tothe extent ythat when the bellyl W ich f in an outer casing, in which,l but-ifor-ft gli' slightv capacity1 for stretching, 'it Ywouldi't pleted condition for servicethat is,vhaving its ends joined or being made lup endlessfthe compression layer, 2, is under ompresr sion, because by its union With the; tension layer, v1, it isv confined to a Width less han that which it had duringvulcanization; the form that the tube naturally assumes Pin crpss-se'ction under these, circumstances being such as shown in Figil 4. "From this, it results that when the tube is inflated, forcingv 'it from the flattened form. shown inAFig. 4 to the circular for shown in Fig. 2, the pression layer, 2, is subjected. The tension pressed by reason o the restraint of the tension layer, 1, the latter layer being V,very

' slightlyV stretched -in coming to the c1rcular\ form, its tractile reaction upon being thus stretched being approximately the measure of the compression to' which the' inner comression layer, 2 is subjectedw The tension layer however,' in elastic'ally extensible to a, slight degree, an the bellyfor inner sideY plained', also l'elasticall extensible,I thetube as an entirety willyiel tothe inlating resstretches readily-toits seat is` thus seated outer or 'tread portion may be stretched :ib the pressure of inflation so, as to seat snu' 'l as the latter withdraws by the strong pressure of. they elastic reaction of said com-- pression layer due to the compression to Which it has been subjected by the restraint of the outer comparatively unstretchable. tension layer, l, acting against the inner inllating pressure, It i s,'however, necessary to guard against theelect which is liable to be produced by a puncturing pointlwhen forced through alayer of rubber which is both quite stretchable and also quite tough. When a-puncturing'. oint,such as that of atack jornail, especia y'if the point is-some-k what blunt, is forcedthrough such rubber, 'the rubber being stretched to a cone-like protrusion at the inner or emerging'sde, be-' y fore it is finally ruptured is liable to rupture* around the base ofsuch cone,'so that a small 'of the tube,

iece 'of thelubber will be punched out odily, the ruptrre occurring suddenly-and the `piece being snapped out by the reaction, instead of the rubber being merely pierced' by the puncturingpoint; and the hole er cavity thus left at the inner1 sideyofthe rub]- ber by the pie e thus' ejected is sometimes `t0o` large to be c'ldsed up by the reaction of4 the rubber from the compression described; es-

pecially since sometimes the'piece thus snapped out will leave 'a hole nearly the, entire thickness of the layer thus pierced. We avoid this danger by making at least. 4

the inner portion of the compression layer' of rubber having a goed percentage of inineral adapted to render it ShOit-bered.

,This rubber is somewhat harder than a purer krubber which, but for the reason above 1ndicate might be used for the' entire ness ofthe compression layer, 14;,but it is`- still suliiciently'gsoft, conpressible and elastic' lto serve well the purpose of closing up the puncture, as, aibove described; and such Qshgrtflibered n ubber 4'noty only will not be VVst'retiihedbythevpuncturing point so as to cllSe a' piece to snap out, as above described, but-ffwhenf itf'forms the inner surface' it iserves to' ypreventthe'stretching of the pori l tion'backQfit, iffthe'latter is of the characftenwhich would thus'bestretched into cone,4 l xform', andthe "resultisi-th'at a' puncturing'g nintfforced through the; entire compression br Without-punchinga piece out "of, it-,`aiid t e 11p.' ehind'the puncturin point as ter withdraws, as above escribedp VItgwill be obvious that the outer tensionU puncture thusmade is completely closed, A

the. a

ayer-emerges 'by merely `piercing the rubs-I,

layer'is -undertension which'would normally l operate to cause a cut or puncture once made to expand, and this tendency 1s much greater vin the semi-hard or semi-vu1canite Whichis employed yfor this tension layer than. it'l would be` in a more nearly pure rubber having greater stretching ca acity. The dan;`

ger of such stretching .o the puncture or vcut in the tension layer is prevented by'ap plying outside of it a layer or skin, l6, o f nearly purerubber haying a .greattensile elasticity ortoughness ;"that -is to say, pure long-fiberd rubber having only a mixture of the necessary elements for proper vulca'nization. This isv the same quality of rubber which it is desirable to employfor the. belly and'` in constructing the tube iti constitutes a continuous layer all around, extending outside the other layers at the tread and constituting the only layer at -the belly or inner side of the tube. n `In the process of constuctionv of the tube,

ythe layer, 6, lis wrappecLneXt to the annular mandrel, 4, 'on which the tire is molded. Theconipr'ession portion, 2, thickened at the tread side, as illustrated? is next applied at the -out'er circumference of?! A the mandrel, 'asclearl'y seeninlfig. eouterLporticn,` atp-fliesst, ci `this compression yiayer,fvviiich is layer, this shorter-fibered portion is appliedin a separate layer, (see Figs. 3 and 4). Vhen the tube th'us molded on the mandrel has been vulcanized the proper degree, it is stripped off the mandrel,-the latter being a l split ring with an opening, fla, permitting such strippingf-by reversing the tube from one end and pulling the reversed portion 4back over the remainder, after the manner of stripping a glove linger off the finger, as illustrated in Fig. 4. This brings the tension layer, 1,'outside the compression layer, 2, the pure rubber skin, 6, being, however, outside the tension layer, and the last-applied short-fibered layer of the compression portion being now the innermost of the several layers at the tread. The tube is completed and rendered endless by telescoping the one end within the other and suitably joining the lapped portions in a manner Well understood and not illustrated in detail.

In order that the several layers may have the characteristics necessary for their coperation as described, we malte them substantially as follows: 0f the compression portion, the innermost layer, 8, whiclnas above described, is short-fibered rubber, is made of about lifty per cent. Para or substantially uivalent rubber forty per cent. mineral fi ler,-zine oxid and Whiting in approximately equal parts,and the remainder of vulcanizing material,-sulfur and litharge in approximately equal parts. The remainder of the compression portion, 2, next inside of the tension layer, 1, may, if preferred, be of a somewhat softer and purer uality of rubber; for example, about sixtytive per cent. pure Para, and corres ondingly less of a rubber compound ma( e up of n'iineral filler. The tension layer consists of fifty per cent. of asbestine or finely reduced or l'nnvdered asbestos fiber, for hardening and toughening the stock, the remainder being substantially pure Para with the necessary vulcanizing material, all the ele'- ments being thoroughly incorporated with nach other in the usual manner of incorpo- )ating mineral fillers with rubber stock for producing;` rubber fabric. The outermost layer. which also extends around to forni the belly, is, as above stated, sul'istantially pure .Para rubber, with only the necessary mixture for vulcanizing materials .Beside the purpose of operating as a tension member for holding the portion, 2, com` pressed, as above described, the layer, l, operates as a partial non-conductor of heat, preventing the'heating and consequent overvulcanizing or hardening of the inner compression portion, and also the increase of pressure Which results from such heating and causes blow-outs. The asbestine or asbestos fiber which is employed, as above described, in said tension layer has this effect upon the properties of said tension layer.

We claim 1. An iniiatable endless tube for a pneumatie tire, Whose side toward the tread comprises an inner portion of relatively soft ands compressible rubber, and outside of said compressible portion a layer of semi-hard rubber, said outer harder layer being normally less in transverse dimension than the inner softer layer and being normally slightly stretched transversely While the inner softer layer is compressed, and an outer skin or layer of highly elastic and tough rubber.

2. An inflatable endless tube for a pneumatic tire, whose side toward the tread comrises an inner layer of relatively soft and compressible rubber of Which the innermost portion is short-fibered, and outside of said inner compressible layer a tension layer of semi-hard rubber having slight stretchability and strong elastic reaction, and being normally less in. transverse dimension than the inner compressible portion, the inner compressible 'portion being normally compressed while the tension layer is normally slightly stretched.

3. An inflatable endless tube for a pneu- .matic tire, Whose side toward the tread comprises an inner portion of relatively soft and eompressible rubber, of which the innermost portion is short-libered; a layer outside said compressible layer composed of semihard rubber slightly stretchable and having strong elastic reaction, and an outer layer or skin of .substantiallyA pure long-libered highly elastic rubber' the inner eompressible portion at the trea coml'nessed and the layers outside it being normally slightly stretched.

In testimony whereof, We have hereunto set our hands, respectively, at Chicago, lllinois, this 29th day of Jnly, 1913.

` XIV M. A. VAIL.

(fr. E. SMITH. lVitnesscs:

' liras. S. BURTON,

M. G. ADY.

side belng normally Itis hereby certified that the name of the `fnrthaentionedlassigneelin Letters Patent No. 1,092,130, granted .March 31%;314, pon the -application-ofyVli-llsstm A.

Vail and Osar E. Smith, ofi' Chicejegglliinoie, foi'- en improvement in .Tnbes Pneumatic Tires was erroneol Written and ri`nted-e}esse-Holden whereas seid l al m,

name should have been written and printed Jesse' Hzdot; and` that I the said Letters Patent should be read with this eerreetion therein that-the same' they conform'to the' record of the case in 4the Patent Office. v

Signed and seeled this 9th day of une, A. D., 1914.

, [SEAL] J. T. NEWTON;

Acting @ammissioner qf 

